1. Field of the Invention
The present invention relates to mixed-signal programmable integrated circuits. More particularly, the present invention relates to a reconfigurable delta sigma analog-to-digital converter and customized digital filters with embedded flash FPGA and flash memory
2. The Prior Art
During the design stage of mixed-signal system, engineers have to understand and predict what kind of analog input signals the system will interface to, and select appropriate analog-to-digital converters. After the analog signals are converted into the digital domain, designers need to use filters for separation of signals that have been combined and restoration of signals that have been distorted during conversion. According to the particular application, system designers have to decide which filters to employ in order to achieve dedicated signal time-domain and frequency-domain characteristic requirements. Choosing the right analog-to-digital converters and filters for a particular application is a challenge that demands high-level mixed-signal design skills and a significant amount of board level design and testing trial and error.
Some companies begin to design devices using field programmable analog arrays such as an FPAA product offered by Anadigm of Oak Park, Calif. In order to achieve reprogrammability of the analog circuitry, the FPAA architecture is built on the switching fabric of a CMOS-based switched-capacitor (SC) network. The core of the device is an array of identical Configurable Analog Blocks (CABs). The FPAA device consists of a matrix of configurable switched-capacitor configurable analog blocks (CABs), enmeshed in a fabric of programmable interconnect resources. These programmable features are directed by an on-chip SRAM configuration memory. The CABs have access to a single Look-Up Table (LUT), which can be used to implement non-linear functions such as user-defined input-to-output transfer functions, and arbitrary signal waveform generation. In addition, some FPAA devices allow designers to implement an integrated 8-bit analog-to-digital converter. This method basically results in configurable but low-end analog functional blocks such as comparators, filters and SAR ADCs.
Traditionally, in order to process different analog input signals, a designer has to choose multiple ADCs/filters and design them into one system. For example, for test equipment like digital oscilloscopes or sensor signal conditioning detectors, the test device has to equipped with multiple signal conditioning boards, since the analog input signal is unknown until the input is connected and measured. Each board has its own data acquisition components such as ADCs and filters to be installed in order to satisfy different requirements of the analog input signals to be encountered. Designers have to use numerous of discrete devices to interface to different analog signals. Such a system is shown in FIG. 1.